Acrylic acid esters

ABSTRACT

N-Substituted acryloyloxyethyl amines are useful both as radiation curable coating materials and as cure accelerators in coating formulations. The amines are prepared by one of several methods including transesterification of acrylate esters with an N-substituted hydroxyethylamine or acrylation of the N-substituted hydroxyethylamine.

This invention relates to novel compounds which accelerate the cure ofvarious classes of known photopolymerizable monomers. In addition, thenovel compounds of this invention can be employed by themselves asphotopolymerizable monomers.

Radiation curable coating compositions are wellknown in the art. Due torestrictions on the amount of solvent permitted in the atmosphere andbecause the energy crisis is forcing industry to find the most efficientsystems available, the search has continued for a 100 percentpolymerizable system, that is, compositions which have no volatilecomponents but contain diluents which react to become either the curedfilm or part of the cured film. Such types of monomers are known; forexample, the polyacrylates, methacrylates and itaconates ofpentaerythritol polyethers disclosed in U.S. Pat. Nos. 3,551,235;3,551,246; 3,551,311; 3,552,986; 3,558,387 and 3,661,614. To increasethe speed of photopolymerization, compounds known as cure acceleratorshave been employed such as those disclosed in U.S. Pat. Nos. 3,551,246;3,551,311; 3,552,986 and 3,759,807. However, these cure accelerators arenot 100 percent polymerizable.

This invention relates to compounds which are 100 percent polymerizable,which cure very rapidly and which also are accelerators for the knownphotopolymerizable monomers. The compounds of this invention have thefollowing structural formula: ##STR1## A is hydrogen or methyl; R isalkyl, for example, lower alkyl such as methyl, ethyl, propyl, butyl,pentyl and the like; cycloalkyl, for example, cyclo lower alkyl such ascyclopentyl, cyclohexyl and the like substituted alkyl, for example,substituted lower alkyl such as substituted ethyl radical of theformula-CH₂ CH₂ X wherein X is cyano, hydroxy, nitro, or a radical ofthe formula CO₂ R¹, COR¹, CONH₂, CONHR¹ or CONR¹ ₂ wherein R¹ is alkyl,for example, lower alkyl such as methyl, ethyl, n-propyl, n-butyl,tert-butyl, pentyl and the like; m is a number having a value of 1 to 2and n is a number having a value of 0 to 1.

When employed as an accelerator, the radiation curable compositionscomprise from about 5 to about 80 percent by weight of an N-substitutedacryloyloxyethylamine (I, supra) and from about 20 to about 95 percentof a photopolymerizable polyfunctional ethylenically unsaturatedcompound.

The preferred compositions of this invention comprise from about 5 toabout 30 percent of an N-substituted acryloyloxyethylamine (I) and fromabout 70 to about 95 percent by weight of at least one ester of anethylenically unsaturated acid of pentaerythritol, dipentaerythritol,dipentaerythritol, polypentaerythritol, trimethylolpropane, ethyleneglycol or neopentyl glycol. The preferred esters are the acrylate,methacrylate and itaconate esters. Specific examples include, but arenot limited to, trimethylolpropane triacrylate, pentaerythritoldiacrylate, pentaerythritol triacrylate, dipentaerythritol triacrylate,pentaerythritol tetraacrylate, dipentaerythritol diacrylate,dipentaerythritol tetraacrylate, dipentaerythritol pentaacrylate,dipentaerythritol hexacrylate, tripentaerythritol octacrylate and thelike; prepolymers of these esters, for example, dimers, trimers andother oligomers and mixtures and copolymers thereof, as well as mixturesof the monomers and prepolymers. The above described esters may beobtained by one of several methods including ester interchange whichcomprises interacting an ester of the acid and a suitable volatilealcohol with a polyhydric alcohol in the presence of a suitable catalystor the esters may be prepared by the direct reaction of a polyhydricalcohol with acrylic acid or an acrylyl halide.

Before exposing the coatings containing the N-substitutedacryloyloxyethylamine (I, supra) and compositions described above toactinic energy there is added a photoinitiator. The photoinitiators orsensitizers are used in amounts of from about 1 to 25% by weight, andpreferably from about 2% to 15% by weight of the total polymerizablecomposition. Preferred photoinitiators include acyloins and derivativesthereof, for example, benzoin alkyl ethers such as benzoin methyl ether,benzoin ethyl ether and the like, desyl halides such as desyl bromide,desyl chloride and the like, desyl amine, benzophenone derivatives,polychlorinated aromatic compounds and mixtures thereof.

Any suitable source of actinic energy may be used, for example, a 2400watt, medium-pressure, mercury arc source. Factors varying the rate atwhich a photopolymerizable composition will dry include the specificingredients in the composition, concentration of the photoinitiators,thickness of the material, nature and intensity of the radiation sourceand its distance from the material, the presence or absence of oxygenand the ambient temperature. The compositions of the present inventionmay be used in relatively thick layers or may be used as thin filmshaving the thickness of from about 0.5 to 150 micons, and preferablyfrom about 1 to 10 microns.

The N-substituted acryloyloxyethylamines (I) are prepared by one ofseveral methods including:

a. the transesterification of a lower alkyl acrylate such as methylacrylate, ethyl acrylate, methyl methacrylate ethyl methacrylate and thelike with an N-substituted bis(hydroxyethylamine) (II) or

b. acrylation of an N-substituted bis(hydroxyethylamine)(II, infra) withan acryloyl halide such as acryloyl chloride and the like or acrylicacid anhydride. The following equation illustrates this process:##STR2## wherein A, R, m and n are as defined above and Z is halo suchas chloro and the like, lower alkoxy such as methoxy, ethoxy and thelike or acryloyloxy.

The N-substituted bis(hydroxyethylamines)(II, supra) employed above areprepared by either of two methods depending upon what R group isdesired. One method comprises treating diethanolamine (III) with asubstituted vinyl (IV). This reaction is conveniently conducted in theabsence of solvents at a temperature in the range of from about 20° to100° C. The following equation illustrates this process: ##STR3##wherein X is as defined above.

By employing the following substituted vinyl compounds (IV, supra)acrylonitrile, ethyl acrylate, methylvinyl ketone, acrylamide, methylacrylate, butyl acrylate and 2-ethylhexyl acrylate and reacting eachwith diethanolamine, there is obtained the corresponding N-substitutedN,N-bis(hydroxyethylamine) (II, supra), which when treated with acompound of the formula ##STR4## wherein Z is as defined above, there isobtained, respectively, the following N-substitutedN,N-bis(acryloyloxyethylamines) (I, supra):N,N-bis(acryloyloxyethyl)-3-aminopropionitrile; ethylN,N-bis(acryloyloxyethyl)-3-aminopropionate; n-butylN,N-bis(acryloyloxyethyl)-3-aminopropionate; methylN,N-bis(acryloyloxyethyl)-3-amino propionate;N,N-bis(acryloyloxyethyl)-4-amino-butan-2-one, andN,N-bis(acryloyloxyethyl)-3-aminopropionamide.

A second method for preparing those N-substituted N,N-bis(hydroxyethylamines) wherein R is alkyl or substituted alkyl or cycloalkyl comprisesethoxylation of a primary amine as illustrated by the followingequation: ##STR5## wherein R² is alkyl, substituted alkyl or cycloalkyl.

The photopolymerizable compositions of the present invention aresuitable as adhesives particularly in the laminating art; as coatingsfor metals, plastics, textiles, paper and glass; as markers for roads,parking lots, airfields and similar surfaces; as vehicles for printinginks, lacquers, and paint; and in the preparation of photopolymerizableelements, i.e., a support having disposed thereon a photopolymerizablelayer of a composition as described herein. Moreover, various dyestuffs,pigments, plasticizers, lubricants and other modifiers may beincorporated to obtain certain desired characteristics in the finishedproducts.

When a photopolymerizable composition of the present invention is usedas an adhesive, at least one of the lamina must be translucent whenultraviolet light is used. When the radiation source is an electron beamor gamma radiation at least one of the lamina must be capable oftransmitting high energy electrons or gamma radiation, respectively, andneither is necessarily translucent to light. Typical laminations includepolymer-coated cellophane to polymer-coated cellophane films, treatedpolyethylene to treated polyethylene films, Mylar to a metal substratesuch as copper, opaque oriented polypropylene to aluminum,polymer-coated cellophane to polypropylene and the like.

The photopolymerizable compositions of the present invention may beutilized for metal coatings and particularly for metals which are to besubsequently printed. Glass and plastics may also be coated, and thecoatings are conventionally applied by roller or spray. Pigmentedcoating systems may be used for various polyester and vinyl films;polymer-coated cellophane; glass; treated and untreated polyethylene,for example, in the form of disposable cups or bottles; and the like.Examples of metals which may be coated include sized and unsized tinplate.

The compositions may be pigmented with organic or inorganic pigments,for example, molybdate orange, titanium white, chrome yellow,phthalocyanine blue, and carbon black, as well as colored with dyes.Stock which may be printed includes paper, clay-coated paper andboxboard. In addition, the compositions of the present invention aresuitable for the treatment of textiles, both natural and synthetic, forexample, in vehicles for textile printing inks or for specializedtreatments of fabrics to produce water repellency, oil and stainresistance, crease resistance and the like. A typical ink formulationwould be 77% resin, 3% photoinitiator and 20% pigment.

Photopolymerizable elements of this invention comprise a support, forexample, a sheet or plate, having superimposed thereon a layer of theabove-described photopolymerizable compositions. Suitable base orsupport materials include metals, for example, steel and aluminumplates, sheets, and foils, and films or plates composed of variousfilm-forming synthetic resins or high polymers, such as additionpolymers, and in particular, vinyl polymers, for example, vinyl chloridepolymers; vinylidene chloride polymers; vinylidene chloride copolymerswith vinyl chloride, vinyl acetate or acrylonitrile; and vinyl chloridecopolymers with vinyl acetate or acrylonitrile; linear condensationpolymers such as polyesters, for example, polyethylene terephthalate;polyamides, and the like. Fillers or reinforcing agents can be presentin the synthetic resin or polymer bases. In addition, highly reflectivebases may be treated to absorb ultraviolet light or a light-absorptivelayer can be transposed between the base and photopolymerizable layer.

Photopolymerizable elements can be made by exposing to ultraviolet lightselected portions of the photopolymerizable layer thereof until additionpolymerization is completed to the desired depth in the exposedportions. The unexposed portions of the layer are then removed, forexample, by use of solvents which dissolve the monomer or prepolymer butnot the polymer.

The invention is illustrated in the following examples, but is notintended to be limited thereto.

EXAMPLE 1 3-[N,N-Bis(acryloyloxyethylamino)]propionitrile Step A -3-[N,N-Bis(hydroxyethylamino)]propionitrile

To a one liter, four-necked, round bottomed flask fitted with athermometer and a "Therm-O-Watch", and ice bath atop a pot-lifter, apressure equalizing addition funnel, a mechanical stirrer and a refluxcondenser is added dry diethanolamine (503 g., 1.79 moles).Acrylonitrile (254 g., 4.79 moles) is added dropwise over a one hourperiod. The temperature of the slightly exothermic reaction is moderatedwith an ice bath and kept between 40°-45° C. Upon completion of theaddition, the reaction temperature is allowed to reach 50° C., and thencooled to ambient temperature (ca. 1.5 hour) to afford3-[N,N-bis(acryloyloxyethylamino)]propionitrile, a clear, slightlyyellow liquid (757 g.), Brookfield Viscosity = 140-150 centipoise (LVNo. 2 spindle, 30 rpm). Infrared analysis of the product shows theconjugated CN band (γ2240 cm) is replaced by unconjugated CN (γ2260 cm).Nmr analysis shows the absence of vinyl protons indicating greater thana 95 % reaction.

STEP B 3-[N,N-Bis(acryloyloxyethylamino)]propionitrile

A two-liter, four-necked, round bottomed flask is fitted with athermometer, a "Therm-O-Watch", an air ebullator, an oil bath stop apot-lifter, a 15 plate Oldershaw Column fitted with a variable take-offdistillation head, a 500 ml. pressure equalizing addition funnel, and amechanical stirrer. The flask is charged with3-(N,N-bis(hydroxyethylamino)propionitrile (415.0 g., 5.24 eq. of OH),ethyl acrylate (786 g., 7.78 mole, 1.5 eq./eq. of OH), di-n-butyl tinoxide catalyst (6.52 g., 0.026 eq., 0.5 eq. % on OH) and MEHQ inhibitor(1.05 g., 0.1 wt. % on total EA to be charged).

Air ebullition is begun and the reaction mixture is heated to reflux(water, presumably from wet EA, is immediately collected and discarded).As the reaction progresses, ethanol is formed causing the vaportemperature to fall below 80° C.; the reaction mixture becomeshomogenous. Distillation is begun at a rate such that the vaportemperature is kept below 80° C. while the volume of the reactionmixture is kept constant by the gradual addition of ethyl acrylate (263g., 2.63 moles). After 10 hours. glc analysis shows the distillate tocontain 213 g. (88.3% conversion of ethanol). At this point, the pottemperature has risen to 115° C. and the vapor temperature to 85° C.(slowing the rate of distillation failed to depress the vapor tempertureindicating that ethanol formation has ceased). The distillation head andOldershaw Column are replaced with a straightlead distillation head. Theapparatus is fitted with a steam inlet tube. An additional 0.5 g. ofMEHQ is added to the reaction mixture and the excess ethyl acrylate isremoved by steam distillation. An azeotrope composed of 85/15//EA/wateris collected. Steam distillation is stopped when the EA component of thedistillate is no longer discernible (pot temperature 95° C.). Theresidual water is distilled at reduced pressure (20 mm) at a maximum pottemperature of 100° C. The product,3-(N,N-bis[acryloyloxyethylamino)]propionitrile (629.2 g., 95% yield,M=1.76, n-0.24) is isolated as a clear, light yellow liquid. EA content= 30-500 ppm, water content = 0.1%, viscosity = 48 centipoise and Br No.= 118.

EXAMPLE 2 Ethyl 3-[N,N-Bis(acryloyloxyethylamino)]propionate

Step A - Ethyl 3-[N,N-bis(hydroxyethylamino)]propionate

By substituting for the acrylonitrile of Example 1, Step A, an equimolarquantity of ethyl acrylate and by following substantially the proceduredescribed therein, there is obtained ethyl3-[N,N-bis(hydroxyethylamino)]propionate. Viscosity = 90 centipoise;hydroxy number = 897 observed/850 theoretical.

STEP B Ethyl 3-[N,N-bis(acryloyloxyethylamino)]propionate

By substituting for the 3-[N,N-bis(hydroxyethylamino)]propionitrile ofExample 1, Step B, an equimolar quantity of ethyl3-[N,N-bis(hydroxyethylamino)]propionate and by following substantiallythe procedure described therein, there is obtained ethyl3-[N,N-bis(acryloyloxyethylamino)]propionate. Viscosity = 80 centipoise,bromine number = 97.7.

EXAMPLE 3 3-[N,N-Bis(acryloyloxyethylamino)]propionamide Step A -3-[N,N-bis(hydroxyethylamino)]propionamide

To a one-liter, four-necked, round bottomed flask fitted with amechanical stirrer, a thermometer, a "Therm-O-Watch" and a condenser isadded diethanolamine (472.5 g., 4.5 moles) and acrylamide (319.5 grams,4.5 moles). The mixture is heated to 60° C. whereupon the contentsbecome homogenous. At this point, a moderate exothermic reaction occurswhich raises the reaction temperture to 100° C. The product,3-[N,N-bis(hydroxyethylamino)]propionamide, is cooled and used in thefollowing step without further purification.

STEP B - 3-[N,N-bis(acryloyloxyethylamino)]propionamide

By substituting for the 3-[N,N-bis(hydroxyethylamino)]propionitrile ofExample 1, Step B, an equimolar quantity of3-[N,N-bis(hydroxyethylamino)]propionamide and by followingsubstantially the procedure described therein, there is obtained3-[N,N-bis(acryloyloxyethylamino)]propionamide.

EXAMPLE 4 4-[N,N-Bis(acryloyloxyethylamino)]butan-2-one Step A -4-[N,N-bis(hydroxyethylamino)]butan-2-one

By substituting for the acrylonitrile of Example 1, Step A, an equimolarquantity of methylvinylketone and by following substantially theprocedure described therein, there is obtained4-[N,N-bis(hydroxyethylamino)]butan-2-one.

Step B - 4-[N,N-bis(acryloyloxyethylamino)]butan-2-one

By substituting for the 3-[N,N-bis(hydroxyethylamino)]propionitrile ofExample 1, Step B, an equimolar quantity of4-[N,N-bis(hydroxyethylamino)]butan-2-one and by following substantiallythe procedure described therein, there is obtained4-[N,N-bis(acryloyloxyethylamino)]butan-2-one.

The following table, taken together with the equations, illustrates thevarious starting materials, intermediate and final products which can beprepared and employed as accelerators with other photopolymerizablemonomers or employed themselves as photopolymerizable monomers. ##STR6##

                  TABLE I                                                         ______________________________________                                        Ex. No. X             Z             A                                         ______________________________________                                        5       CN            Cl            CH.sub.3                                  6       CN            OCH.sub.3     H                                         7       CO.sub.2 CH.sub.3                                                                           OC.sub.2 H.sub.5                                                                            CH.sub.3                                  8       CO.sub.2 C.sub.2 H.sub.5                                                                                  H                                         9       CO.sub.2 C.sub.3 H.sub.7                                                                    OC.sub.2 H.sub.5                                                                            H                                         10      CO.sub.2nC.sub.4 H.sub.9                                                                    OC.sub.2 H.sub.5                                                                            H                                         11      COCH.sub.3    OC.sub.2 H.sub.5                                                                            CH.sub.3                                  12      COC.sub.2 H.sub.5                                                                           OC.sub.2 H.sub.5                                                                            CH.sub.3                                  13      COC.sub.3 H.sub.7                                                                           OCH.sub.3     H                                         14      NO.sub.2      Cl            H                                         15      CONHCH.sub.3  OC.sub.2 H.sub.5                                                                            H                                         16      CON(CH.sub.3).sub.2                                                                         OC.sub.2 H.sub.5                                                                            H                                         ______________________________________                                    

EXAMPLE 17 N-Hydroxyethyl-N,N-bis(acryloyloxyethyl)amine

To a one liter, four-necked, round bottomed flask equipped with athermometer, "Therm-O-Watch," air ebullator, oil bath stop a pot lifter,a fifteen plate Oldershaw column fitted with a variable take-offdistillation head, 500 ml. pressure-equalizing addition funnel and amechanical stirrer is added dry triethanolamine (50 g., 0.336 mole), dryethyl acrylate (300 g., 3 moles), hydroquinone monomethyl ether (MEHQ)(0.38 g., 0.13 wt. % on monomer) and dibutyl tin oxide catalyst (1.92g., 0.008 mole). The reaction mixture is heated to reflux while gentleair ebullition is maintained. As the reaction proceeds, the vaportemperature falls below 80° C.; distillation is begun and maintained ata rate such that the vapor temperature is kept below 80° C. The potvolume is kept approximately constant by the addition of fresh ethylacrylate. The ethanol content of the distillate is measured by glcanalysis. After 11 hours, the total ethanol distilled reaches 0.67 mole(m = 2.0) and the reaction is terminated. The Oldershaw column anddistillation head are replaced with a straight-lead distillation headand the excess ethyl acrylate removed under vacuum during which airebullition is maintained to prevent polymerization. The maximum pottemperature is 100° C. The product is isolated as a clear, liquid,viscosity, 55 centipoise.

Infrared spectrum:

γ3400-3600 cm-1 (broad, OH)

γ1740 cm-1 (C=O)

γ1660 cm-1 (C=C, doublet)

γ800 cm-1 ##STR7##

Nmr analysis shows the reaction conversion to be 66% (m = 2.0, n = 0.0).

The following Table II taken together with the following equationillustrates the various starting materials and final products which maybe prepared by following substantially the procedure in Example 17:##STR8##

                  TABLE II                                                        ______________________________________                                                                           Viscosity                                  Ex. No.                                                                              R             M       N     (Brookfield)                               ______________________________________                                        18     (CH.sub.3).sub.3 C                                                                          1.3     0.7   20 centipoise                              19     (CH.sub.3).sub.3 C                                                                          2       0     25 centipoise                              20                                                                                                 1.6     0.4   40 centipoise                              21                                                                                    ##STR9##     1.9     0.1   Not determined                             22                                                                                    ##STR10##    1.55    0.45  Not determined                             ______________________________________                                    

The compounds of Examples 17-22 are all liquids of low viscosity. Thevalues for m and n are obtained from nuclear magnetic resonance spectraby the relative areas (integrated) of the proton absorption centered atδ4.3 ppm ##STR11## triplet) versus the proton absorption centered atδ3.6 ppm (CH₂ OH). The percent conversion is calculated as follows:##EQU1##

The products are further characterized by infrared spectroscopy and showcharacteristic absorptions at γ 1740 cm⁻ ¹ (carbonyl, ester), 1650 cm⁻ ¹(doublet, C=C) and 800 cm⁻ ¹

What is claimed is:
 1. A compound of the formula:wherein A is hydrogenor methyl; R is a radical of the formula -CH₂ CH₂ X wherein X is,hydroxy or nitro; m is a number having a value in the range of 1 to 2and n is a number having a value in the range of 0 to
 1. 2. A compoundaccording to claim 1 wherein A is hydrogen and X is hydroxy.
 3. Acompound according to claim 1 wherein A is hydrogen; X is hydroxy; mequals 2 and n equals 0.